The "2-Bits" V-Twin

[RReid]

Thanks Steve.

[Craig DeShong]

 Wry nice Ron, it runs beautifully.

[RReid]

Thanks Craig! Hope you have a good time at Rough & Tumble.

[Brian Rupnow]

So Mr. Reid---how did you set the valve timing on your engine? I am setting mine up so that when one cylinder is on the power stroke, the other cylinder is on the intake stroke---more or less. Actually, I'm setting it up as if the two cylinders are completely independent of each other.  When the first cylinder is set up, I will then set the second cylinder up the same way I set up the first cylinder. As far as I can see, there are only two ways to do this valve timing thing. Either correctly, as I have outlined, or 360 degrees out of phase. I have no trouble setting up a dual opposed cylinder engine, nor a twin cylinder engine with both cylinders side by side, but this 50 degree difference in the two cylinders has me questioning myself.---Brian

[RReid]

Hi Brian. I agree, it can get confusing. I set up an assembly drawing in my CAD that allows me to rotate the crank and watch the pistons go up and down in the cylinders. I even had a degree wheel on it at one point. It really made it much easier to visualize the relationship between the two motions.

I call the cylinder that would be to the front in a motorcycle cylinder #1. Crankshaft rotation is counterclockwise viewed from the left side. At TDC on #1's power stroke, cylinder #2 in part way into the intake stroke, which is basically what you said also. When cylinder #2 is at TDC on its power stroke, cylijder #1 will be near the end of its exhaust stroke.

In my case, valve timing was easy. Since the intake valve is atmospheric, there is no timing to set for it.  The exhaust valve lives in the cylinder jacket, not the head. So to set that I just took the head off and visually set it so that the valve was just opening at BDC of the power stroke, and verified that it was closed at the end of the exhaust stroke. No overlap. Almost like cheating, I know.

[Brian Rupnow]

Thank you R Reid. My engine turns clockwise when viewed from the flywheel side. I'm going to set my cylinders up to have valve opening and closing happen as if each cylinder was on a one cylinder engine. If I do this right, each cylinder will operate with no "knowledge" that there is a second cylinder on the engine. This may sound a bit odd, but I think it will work.---Brian